Clinical application of regenerative medicines has been studied recently, and induction of differentiation of pluripotent stem cells such as iPS cell and ES cell into desired cells has been actively pursued. In fact, clinical tests using ES cell-derived RPE (retinal pigment epithelium) cell for Stargardt disease and dry age-related macular degeneration has already been started. In addition, clinical tests using autologous iPS cell (iPSC)-derived RPE cell for wet age-related macular degeneration are designed by some groups.
However, pluripotent stem cells such as iPS cell and ES cell often show canceration during their growth, and differentiated cells derived from pluripotent stem cell need to be carefully evaluated for the presence or absence of tumor formation caused by the remaining undifferentiated iPS cell and ES cell. This poses the largest problem in transplantation of autologous iPSC-derived cells and tissues free of immunological barriers. That is, it is extremely important for practicalization of differentiation-induced cells and tissues to remove remaining undifferentiated cells and purify differentiated cells. The present inventors reported a method of highly sensitively detecting iPS cells remaining in iPSC-derived RPE cells (non-patent document 1). However, a method of more efficiently removing remaining undifferentiated cells in vitro has been desired.
In the meantime, cytokine, extracellular matrix, complement factor and the like secreted by pluripotent stem cells and differentiated cells derived therefrom have also been studied. Of these, PEDF (pigment epithelium-derived factor) is a 50 kDa secreted protein also known as Serpin F1, which was found as a protein secreted by RPE cell, and is a factor having an angiogenesis suppressive action (non-patent document 2) and a neuroprotection action (non-patent document 3). Secretion of PEDF is found not only in RPE cells but also adipocytes, hepatocytes and dendritic cells (BioGPS site). Also, PEDF is known to induce apoptosis in cancer cells (non-patent document 4), vascular endothelial cells (non-patent document 5) and human umbilical vein endothelial cells (HUVEC) (non-patent document 6) and, as induction pathways of these apoptosis, FAS/FASL pathway (non-patent document 4) and p38 MAPK pathway can be mentioned (non-patent document 5). However, a direct influence of PEDF on undifferentiated cells has not been known well.